Process for separating methanol and methyl (meth)acrylate

Abstract

The present invention relates to a process for producing a distillation product having a methanol concentration greater than the methanol concentration in the minimum boiling azeotrope of methanol and methyl (meth)acrylate from a mixture having a methanol concentration less than the methanol concentration in the minimum boiling azeotrope of methanol and methyl (meth)acrylate in a distillation column, and additionally provides a trans-esterification process for preparing C6- to C 22 alkyl, aryl or alkenyl esters from methyl (meth)acrylate.

Description

TECHNICAL FIELD

[0001] The present invention relates to a process for breaking the azeotrope of methanol and methyl (meth)acrylate and additionally provides a process for the preparation of C6- to C 22 - trans-esterification of alkyl, aryl or alkenyl esters of (meth)acrylic acid.

[0002] The term "breaking the azeotrope of methanol and methyl (meth)acrylate" as used in the context of the present invention means a process for producing a distillation product having a concentration of methanol which is greater than the concentration of methanol in the minimum boiling azeotrope of methanol and methyl (meth)acrylate from a mixture having a concentration of methanol which is less than or equal to the concentration of methanol in the minimum boiling azeotrope of methanol and methyl (meth)acrylate in a distillation column. BACKGROUND

[0003] Alkyl, aryl or alkenyl esters of (meth)acrylic acid are usually prepared by trans-esterification of methyl (meth)acrylate with the corresponding alcohol.

[0004] The trans-esterification of methyl (meth)acrylate with an alcohol results in methanol which is usually recovered in the form of a mixture of methanol and methyl (meth)acrylate by distillation. The resulting distillate can have the same high concentration of methanol as the azeotropic composition, but it is typically below this maximum. This leads to an undesired loss of methyl (meth)acrylate. The distillate thus obtained has to be subjected to further processing steps in order to separate and re-use the methyl (meth)acrylate. For economic reasons it would be particularly desirable if the effects of azeotrope formation could be mitigated so that the loss of methyl (meth)acrylate in the distillation product is reduced.

[0005] In view of the above, it is an object of the present invention to provide a process for breaking the azeotrope of methanol / methyl (meth)acrylate which is either a process independent of any trans-esterification reaction or a part of an improved process for the separate preparation of alkyl, aryl or alkenyl esters of (meth)acrylic acid by trans-esterification, wherein the amount of methyl (meth)acrylate in the distillate can be significantly reduced so that the effort for the further separation steps currently required for the distillate can be reduced or even avoided. SUMMARY

[0006] This object is solved for alkyl, aryl or alkenyl esters of (meth)acrylic acid having a linear or branched, acyclic or cyclic alkyl, aryl or alkenyl group having 6 to 22 carbon atoms by the process according to the present invention.

[0007] The inventors have surprisingly found that if the trans-esterification of methyl (meth)acrylate with the corresponding C6- to C 22- alcohol feed treatment azeotrope, the methanol concentration in the distillate will then exceed the azeotropic concentration of methanol (i.e. the azeotrope is broken) and the (meth)acrylic acid methyl ester is depleted in the distillate material, in contrast to the C6- to C 22 - enrichment of the alcohol material. As a result, the methanol concentration in the distillate rises sharply and reaches a (meth)acrylic acid methyl ester concentration which is significantly lower than the azeotropic concentration of (meth)acrylic acid methyl ester. Thereby, the efficiency of the process is significantly improved with respect to the (meth)acrylic acid methyl ester yield.

[0008] Thus, the present application provides a process for breaking the azeotrope of methanol and (meth)acrylic acid methyl ester, i.e. a process for producing a distillate having a methanol concentration greater than the concentration of methanol in the minimum boiling azeotrope of methanol and (meth)acrylic acid methyl ester from a mixture of methanol and (meth)acrylic acid methyl ester having a methanol concentration less than or equal to the concentration of methanol in the minimum boiling azeotrope of methanol and (meth)acrylic acid methyl ester in a distillation column, wherein the process comprises the step of contacting the mixture of methanol and (meth)acrylic acid methyl ester having a methanol concentration less than or equal to the concentration of methanol in the minimum boiling azeotrope of methanol and (meth)acrylic acid methyl ester with an alcohol of formula (I)

[0009] HO-R 1 (I),

[0010] wherein R 1 is a linear or branched, acyclic or cyclic alkyl, aryl or alkenyl group having 6 to 22 carbon atoms, which is added by an alcohol feed located at the distillation column.

[0011] Further, the present application relates to a process for preparing a (meth)acrylic acid ester of formula (II)

[0012] CH2=C(R 2 )-CO-OR 1 (II)

[0013] wherein R 2 is hydrogen or methyl, and

[0014] R 1 is a linear or branched, acyclic or cyclic alkyl, aryl or alkenyl group having 6 to 22 carbon atoms,

[0015] by reacting a (meth)acrylic acid methyl ester of formula (III) with an alcohol of formula (I)

[0016] CH2=C(R 2 )-CO-OMe (III)

[0017] wherein R 2 is as defined above,

[0018] HO-R1 (I)

[0019] wherein R 1 as defined above;

[0020] wherein methanol produced by the transesterification reaction is separated from the methyl (meth)acrylate of formula (III) using a distillation column at a methanol concentration less than or equal to the methanol concentration in the azeotrope composition of methanol and the methyl (meth)acrylate of formula (III); and the mixture thus obtained is enriched to a methanol concentration greater than the concentration of methanol in the azeotrope composition of methanol and the methyl (meth)acrylate of formula (III) by further adding the alcohol of formula (I) via an alcohol feeder located at the distillation column.

[0021] The process according to the present application can be carried out batchwise, or alternatively, in a continuous manner. DETAILED DESCRIPTION

[0023] The distillation column used in the process of the present application is preferably an extractive distillation column. The extractive distillation column can comprise, in addition to its extractive section, a rectifying section and / or a stripping section.

[0024] In one embodiment of the present application, the extractive distillation column is divided into three sections: (1) a rectifying section between the top of the column and the alcohol feeder location, (2) an extractive section between the alcohol feeder location and the azeotrope feeder location, and (3) a stripping section located below the azeotrope feeder location.

[0025] In a different embodiment of the present application, the extractive distillation column has two sections: (1) a rectifying section between the top of the column and the alcohol feeder location, and (2) an extractive section between the alcohol feeder location and the azeotrope feeder location.

[0026] In the process according to the present application, the alcohol feeder is located at the distillation column, for example at the top of the distillation column, or alternatively, in the top region of the distillation column.

[0027] Preferably, the alcohol feeder is located in the top region of the distillation column. As used in the context of the present application, the term "top region of the distillation column" refers to a location in the extractive distillation column where the number of separation trays in the extractive section is greater than or equal to the number of separation trays in the rectifying section.

[0028] However, feeding the alcohol to the top of the column can result in loss of the alcohol used as extractant. Therefore, the alcohol is advantageously fed near the top of the distillation column, i.e. in the top region, see above, so that the separation capacity of the extractive section is maximized while providing sufficient rectification to avoid excessive loss of alcohol. In other words, the preferred location of the alcohol feeder gives enough column height for extraction.

[0029] Preferably, above the alcohol feed there are a minimum of 0.01 theoretical separation plates and to avoid undesirable enrichment back into the azeotrope there are a maximum of 10 theoretical separation plates.

[0030] The alcohol of the formula (I) can be added, for example, by means of an alcohol feed, at temperatures between 0°C and 70°C.

[0031] The addition of the alcohol of the formula (I) by means of a distillation column can take place discontinuously or continuously.

[0032] In order to prevent undesirable polymerization of the (meth)acrylates, polymerization inhibitors can be used in the process according to the application. Advantageously, these processes are carried out in the presence of an inhibitor composition which comprises or consists of at least one phenolic polymerization inhibitor.

[0033] These compounds, for example hydroquinone, hydroquinone ethers such as hydroquinone monomethyl ether or di-tert-butyl hydroquinone, phenothiazine, N,N'-(diphenyl)-p- phenylenediamine, 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, p-phenylenediamine, methylene blue or sterically hindered phenols, are widely known in the art. These compounds can be used individually or in the form of mixtures and are generally commercially available. The mode of action of the stabilizers is generally that they act as free-radical scavengers for the free radicals generated in the polymerization. The proportion of the inhibitors, whether individually or as mixtures, can generally be 0.001-0.5% (wt / wt) based on the weight of the total reaction mixture.

[0034] These polymerization inhibitors can be added respectively before or at the start of the reaction or distillation. Furthermore, a small proportion of the polymerization inhibitors employed can be introduced during the transesterification. Processes in which part of the polymerization inhibitors are added by means of reflux in the column are of particular interest here. It is particularly advantageous to use mixtures containing methyl (meth)acrylate, hydroquinone monomethyl ether and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, inter alia. This measure can in particular avoid undesirable polymerization in the distillation column.

[0035] Furthermore, gaseous oxygen can be used for the inhibition. This can be used, for example, in the form of air, wherein the amount introduced should advantageously be such that the content in the gas phase above the reaction mixture remains below the limiting oxygen concentration of the explosion region. It is particularly preferred to use an amount of air in the range from 0.05 to 0.5 liters per hour and per mole of the berol. It is likewise possible to use inert gas / oxygen mixtures, for example nitrogen / oxygen or argon / oxygen mixtures.

[0036] In a particular embodiment of the application, a combination of oxygen and hydroquinone monomethyl ether (HQME) can be used for the inhibition.

[0037] Alternatively, the process according to the application can be carried out in the presence of an inhibitor composition comprising or consisting of a polymerization inhibitor selected from 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2-diphenyl-1- picrylhydrazyl, phenothiazine, N,N'-diphenyl-p-phenylenediamine, aniline black, p- benzoquinone and copper-iron reagent, optionally in combination with a phenolic polymerization inhibitor.

[0038] In the context of the present application, the term "(meth)acrylic alkyl, aryl or alkenyl ester" is to be understood as meaning alkyl, aryl or alkenyl esters of methacrylic acid and acrylic acid.

[0039] In the alkyl, aryl or alkenyl ester of (meth)acrylic acid of formula (II) and the alcohol of formula (I), R 1 may be selected independently from linear or branched, acyclic or cyclic alkyl, aryl or alkenyl groups having 6 to 22 carbon atoms. The term "cycloalkyl" means monocyclic or polycyclic alkyl species and thus includes bicyclic groups such as isobornyl. Preferably, R 1 is a linear or branched, acyclic or cyclic alkyl, aryl or alkenyl group having 7 to 20, advantageously 8 to 18 carbon atoms.

[0040] R 1 groups are to be understood as meaning, for example, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, 2-octyl, 2-ethylhexyl, nonyl, 2-methyloctyl, 2-tert- butylheptyl, 3-isopropylheptyl, decyl, undecyl, 5-methylundecyl, dodecyl, stearyl and / or behenyl, and / or cycloalkyl groups such as cyclohexyl, tert-butylcyclohexyl, cycloheptyl, cyclooctyl, bornyl and / or isobornyl. Furthermore, R 1 groups can be optionally substituted (C6-C 14 )-aryl-(C1-C8)-alkyl, preferably preferably (C6-C 12 )-aryl-(C1-C4)-alkyl, such as, for example, benzyl, naphthylmethyl, naphthylethyl, 2-phenylethyl, 2-phenoxyethyl, 4-phenylbutyl, 3-phenylbutyl, 2-phenylbutyl and / or 2-biphenylylethyl.

[0041] The methyl (meth)acrylate of the formula (III) can be introduced into the trans- esterification process according to the present application as pure substance, or for example as a mixture containing a methanol concentration less than or equal to the azeotrope composition (from the previous reaction), or as a combination of fresh / pure methyl (meth)acrylate of the formula (III) with a mixture of methyl (meth)acrylate of the formula (III) and methanol having a methanol concentration less than or equal to the azeotrope composition of methanol and methyl (meth)acrylate of the formula (III). Such a process setup is particularly suitable for a trans-esterification process carried out in continuous mode.

[0042] The process according to the present application can for example also be implemented in a stand-alone device. Any alcohol (i.e. alcohol of the formula (I)) which does not form an azeotrope with the (meth)acrylate of the formula (III) is added to the first column to break the azeotrope. Then, in the second column, the methyl (meth)acrylate of the formula (III) is separated from the alcohol of the formula (I) which is then reused in the first column.

[0043] In a batch process, the azeotrope can be fed to the reactor before the alcohol and kept boiling under total reflux. Then, the desired alcohol for the reaction is fed to the column. As this alcohol extracts the methyl (meth)acrylate of the formula (III) from the boiling azeotrope, it also starts the trans-esterification reaction.

[0044] In a particularly preferred embodiment of the present application, the (meth)acrylate of the formula (II) is 2-ethylhexyl (meth)acrylate, the methyl (meth)acrylate of the formula (III) is methyl methacrylate, and the alcohol of the formula (I) is 2- ethylhexanol.

[0045] The molar ratio of the alcohol of the formula (I) to the (meth)acrylate of the formula (III) fed to the trans-esterification reactor is preferably in the range of 10:1 to 1 :10, more preferably in the range of 1 :1 to 1 :5, most preferably in the range of 1 :1.1 to 1 :2.5. The latter ratio is particularly suitable for a continuous trans-esterification process.

[0046] In a preferred embodiment of the present application, after the initial reaction period, an additional amount (or the remaining equivalent) of alcohol (I) is introduced into the reaction mixture via the distillation column to enrich the methanol to a concentration greater than the methanol concentration in the azeotrope.

[0047] The addition of alcohol (I) via the distillation column can start directly after the start of the trans-esterification, or alternatively, after the reaction has reached a steady state. In a batch process, the alcohol feed to the distillation column can start at the beginning of the batch or at some point in time after the batch.

[0048] For catalyzing the transesterification of the present application, catalysts selected from the group of alkyl titanates (e.g. tetraisopropyl titanate, tetra(ethylhexyl) titanate), zirconium acetylacetonate, dialkyl tin compounds, lithium compounds (e.g. lithium oxide, lithium hydroxide, lithium chloride, lithium amide (LiNH2), lithium alcoholate (preferably LiOMe), calcium compounds (e.g. calcium oxide and calcium hydroxide), or acids (e.g. p-toluenesulfonic acid, sulfuric acid, methanesulfonic acid) can be used, either alone or using any combination of the above mentioned catalysts.

[0049] Particularly suitable catalysts are e.g. tetraisopropyl titanate, tetra(ethylhexyl) titanate and zirconium acetylacetonate. Catalysts can be purchased in ready-to-use form or can be prepared on site. Alternatively, catalysts can be obtained by recycling from downstream processing.

[0050] Advantageously, 0.2 to 10 millimoles, more preferably 0.5 to 8 millimoles of catalyst per mole of alcohol of formula (I) can be used.

[0051] The reaction time depends, inter alia, on the parameters selected, such as pressure and temperature. However, they are generally in the range of 1 to 24 hours, preferably 5 to 20 hours, very particularly preferably 6 to 18 hours. In the case of a continuous process, the reactor residence time is generally in the range of 1 to 24 hours, preferably 2 to 20 hours, very particularly preferably 2.5 to 10 hours.

[0052] The reaction can preferably be carried out with stirring, wherein the stirring rate is particularly preferably in the range of 50 to 2000 rpm, very particularly preferably in the range of 100 to 500 rpm.

[0053] A suitable apparatus for carrying out the transesterification of the present application can be, for example, a stirred tank reactor with stirrer, steam heater, distillation column (azeotrope column) and condenser. The size of the apparatus depends on the amount of alkyl (meth)acrylate to be prepared, and the process according to the present application can be carried out on laboratory scale (reactor volume 0.5-20 liters) or particularly advantageously on industrial scale. In a particular aspect, the stirred tank reactor can accordingly have a tank volume in the range of 0.25 m 3 to 50 m 3 , preferably 1 m 3 to 50 m 3 , more preferably 3 m 3 to 25 m 3 . The stirrer of the reactor tank can be configured, inter alia, in the form of an anchor stirrer, an impeller, a paddle stirrer or a helical ribbon stirrer.

[0054] The distillation column (azeotrope column) can have one, two or more separation stages. The number of separation stages refers to the number of trays in a trayed column, or to the number of theoretical plates in the case of a column with structured packing or a column with random packing.

[0055] Examples of multistage distillation columns with trays include those such as bubble cap trays, sieve trays, rectangular bubble cap trays, float valve trays, slot trays, slotted orifice trays, bubble cap orifice trays, jet trays, centrifugal trays.

[0056] Examples of multistage distillation columns with random packing are those such as Raschig rings, super-raschig rings, Lessing rings, Pall rings, Berl saddles, Intalox saddles; and examples of multistage distillation columns with structured packing are those such as Mellapak type (Sulzer), Mellapak Plus, Rombopak type (Kühni), Montz-Pak type (Montz). Preferably, there are a minimum of 0.01 theoretical separation trays above the alcohol feed and, to avoid undesirable enrichment back to the azeotrope composition, there are a maximum of 10 theoretical separation trays.

[0057] It is also possible to use distillation columns with a combination of different internals, for example structured packing in a first column section and trays or random packing in a second column section.

[0058] After the end of the reaction, the resulting (meth)alkyl acrylate in many cases already meets the general requirements of the corresponding (meth)acrylate alkyl ester product, which makes further purification in many cases unnecessary. However, it is also possible to isolate the product after the end of the reaction by distillation.

[0059] In order to further improve the quality, in particular in order to remove catalyst, the resulting mixture can be purified by known methods. Due to the tendency of the monomers to polymerize, it is reasonable to use a distillation method which minimizes the thermal stress on the substance to be distilled. Very suitable apparatuses are those in which the monomers are continuously evaporated from a thin layer, such as falling-film evaporators and evaporators with a rotating wiper system. Short-path evaporators can also be used. For example, it is possible to carry out a distillation in which a continuous evaporator with a rotating wiper system and a connected column can be used. By way of example, such a distillation can be carried out at a pressure in the range from 1 to 60 mbar and an evaporator temperature (surface temperature of the falling-film evaporator) of from 60°C to 130°C.

[0060] In the following, the application is illustrated by non-limiting examples and exemplary embodiments. DETAILED DESCRIPTION

[0061] Example:

[0062] Comparative Example 1:

[0063] In a continuous transesterification reaction system consisting of a reactor equipped with azeotrope column and additional columns for the treatment of the continuously withdrawn reactor crude product, unreacted raw materials were separated and recovered from the reactor crude product, and alcohol, MMA and catalyst (titanium (IV) alkoxide) were continuously supplied to the reactor. The reactants were introduced into the reactor. In the example of the present application, 2-ethylhexanol was used as the alcohol. Methanol produced by the conversion of the reaction was continuously withdrawn from the reactor in the form of a mixture containing methanol at a concentration lower than or equal to the azeotropic concentration of methanol, through the azeotrope column. In order to evaluate the concentration during the operation, the density of the distillate was measured and recorded in real time, and was used to calculate the ratio of methanol and MMA (temperature-corrected density according to pure substances). Due to the thermodynamic limitation of the azeotrope on the separation performance, the concentration at the top of the column was typically 78% by weight of methanol. After reaching a steady state, a sample of the recovered methanol distillate was withdrawn and analyzed. The results are reported in Table 1.

[0064] Example 1:

[0065] In a continuous transesterification reaction system consisting of a co-boiling column and an additional column for processing the continuously withdrawn reactor crude product, unreacted starting materials are separated and recovered from the crude product, the alcohol, MMA and catalyst (titanium (IV) alkoxide) are continuously supplied to the reactor. The reactants are introduced into the reactor and the feed point of the alcohol is moved to a position near the top of the co-boiling column without preheating the alcohol. The temperature of the alcohol is 20°C. Arranged above the alcohol feed point is a structured packing element with a theoretical separation capacity of about 0.8 tray. In this example, 2-ethylhexanol is used as the alcohol. Methanol produced by the reaction conversion is continuously withdrawn from the reactor in the form of a mixture containing methanol in a concentration below the azeotropic concentration of methanol through the co-boiling column. In order to assess the concentration during operation, the density of the distillate is measured and recorded in real time and used to calculate the ratio of methanol and MMA (temperature-corrected density according to pure substances). The reactor is started according to Comparative Example 1 and, after reaching a steady state, the feed point of the alcohol is changed as described above. The concentration of methanol in the distillate reacts significantly to the change in the feed point within 2 minutes, the recovered methanol distillate is assumed to have a methanol concentration of greater than 78% by weight. Half an hour later, the first sample of distillate is withdrawn with a calculated concentration of 90% by weight of methanol; the analysis determines largely the same. The second sample after 2 h and a calculated purity of 93% by weight has an analytical methanol content of 92.7% by weight, and the third sample after 4 h after reaching a steady state of 94.5% by weight of methanol has an analytical methanol content of 93.25% by weight. With the enrichment of methanol in the distillate, the total amount of distillate withdrawn decreases. According to the lower concentration of MMA withdrawn in the co-boiling, the feed of MMA into the reactor is reduced after reaching a steady state. The top temperature of the column remains unchanged. At the bottom steam inlet of the column, the temperature drops by 20°C, from 94°C to 74°C. The pressure difference in the column remains unchanged.

[0066] Table 1

[0067]

[0068] Example 2:

[0069] In a glass flask (V = 3 L) equipped with a stirrer, an electric heating mantle and a mirror image random packed column (bottom section height = 0.3 m, diameter = 45 mm, top section height = 0.7 m, diameter = 30 mm), a condenser and a reflux distributor, initially 1.8 kg of a mixture of 75 wt% MeOH and 25 wt% MMA is filled. Additionally air is bubbled into the reactor contents at 2 NL / h. The mixture is stabilized with 1000 ppm by weight of HQME and 50 ppm by weight of Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl). A thermocouple for monitoring the temperature is placed in both the flask and the top of the column. The mixture in the flask is heated to boiling, at the top of the column a reflux:distillate withdrawal ratio of 1 :1 is established at the reflux distributor. After reaching a stable top temperature, the distillate collected is sampled and analyzed by GC.

[0070] After another 15 minutes, 2-ethylhexanol is added at 8 g / min at the top of the column with reflux using an HPLC pump and a coriolis mass flowmeter. The distillate obtained is again sampled and analyzed after 10 and 45 minutes. The reflux:distillate withdrawal ratio of 1 :1 is kept constant.

[0071] Example 3:

[0072] The procedure according to example 2 is followed, but isodecanol is added as the alcohol at 7 g / min.

[0073] Example 4:

[0074] The procedure according to example 2 is followed, but C13.0 alcohol (Lorol Spezial) is added as the alcohol at 6 g / min.

[0075] Example 5:

[0076] The procedure according to example 2 is followed, but cyclohexanol is added as the alcohol at 7 g / min.

[0077] Comparative example 2:

[0078] The procedure according to example 2 is followed, but n-butanol is added as the alcohol at 7.3 g / min.

[0079] The results of the distillate analysis of the experiments are summarized in table 2.

[0080] Table 2

[0081]

[0082] It is clear that without the addition of alcohol at the top of the column, a composition is obtained that is close to the azeotropic composition of MMA and MeOH (about 85.5 wt% MeOH and 14.5 wt% MMA at 1013 mbar), see reference without added alcohol.

[0083] By contrast, alcohols with a polarity sufficiently low (e.g. C n H 2n+1 -OH, n > 6; C n H 2n-1 -OH, n > 6 or C n H 2n-7 -OH, n > 6) have a normal boiling point greater than the normal boiling point of MMA (100°C), which selectively extracts the MMA from the mixture of methanol and MMA in the bottom of the column and thus causes the methanol concentration to exceed the azeotropic concentration of methanol, thereby further enriching the methanol.

[0084] By contrast, more polar short chain alcohols (Comparative Example 2) do not produce a distillation product with a methanol concentration greater than the concentration of methanol in the minimum boiling azeotrope of methanol and methyl methacrylate.

Claims

1. A mixture of methanol and methyl methacrylate, wherein the concentration of methanol is less than or equal to the concentration of methanol in the minimum boiling point azeotrope of methanol and methyl methacrylate, for use in a distillation column. A method for producing a distillation product with a methanol concentration greater than that of the methanol in the azeotrope of methanol and methyl methacrylate at their minimum boiling points. The method is characterized in that it comprises a mixture of methanol and methyl methacrylate in which the methanol concentration is less than or equal to the concentration of methanol in the minimum boiling point azeotrope of methanol and methyl methacrylate. Steps involving contact with alcohols of formula (I): HO-R 1 (THE), Where R 1 It is a straight-chain or branched alkyl group having 6 to 22 carbon atoms. The alcohol is added via an alcohol feeder located in the top region of the distillation column.

2. The method according to claim 1, Its features The distillation column used is an extractive distillation column having at least an extraction section and a rectification section; and the alcohol feeder is located therein such that the number of separation trays in the extraction section is greater than or equal to the number of separation trays in the rectification section.

3. The method according to any one of claims 1 to 2, Its features Above the alcohol feeder, there are theoretical separation trays with a minimum of 0.01 and a maximum of 10.

4. The method according to any one of claims 1 to 2, Its features The alcohol of formula (I) is added through the alcohol feeder at a temperature of 0°C to 70°C.

5. The method according to any one of claims 1 to 2, Its features The method is performed intermittently, or the method is performed continuously.

6. A method for preparing (meth)acrylates of formula (II) CH2=C(R 2 )-CO-OR 1 (II) Where R 2 It is hydrogen or methyl, and R 1 It is a straight-chain or branched alkyl group having 6 to 22 carbon atoms. By reacting methyl methacrylate of formula (III) with an alcohol of formula (I). CH2=C(R 2 )-CO-OMe(III) Where R 2 It is as defined above. HO-R 1 (THE) Where R 1 It is as defined above; in Using a distillation column Methanol produced via transesterification is separated from methyl methacrylate of formula (III) at a methanol concentration less than or equal to that of the azeotropic composition of methanol and methyl methacrylate of formula (III); and The resulting mixture is enriched to a concentration of methanol greater than that of the azeotropic composition of methanol and methyl methacrylate of formula (III) by further adding the alcohol of formula (I) via an alcohol feeder located in the top region of the distillation column.

7. The method according to claim 6, Its features The distillation column used is an extractive distillation column having at least an extraction section and a rectification section; and the alcohol feeder is located therein such that the number of separation trays in the extraction section is greater than or equal to the number of separation trays in the rectification section; and / or Its features Above the alcohol feeder, there are theoretical separation trays with a minimum of 0.01 and a maximum of 10.

8. The method according to claim 6 or 7, Its features The method is performed intermittently, or the method is performed continuously.

9. The method according to any one of claims 6 to 7, Its features After the reaction reaches a stable state, the alcohol of formula (I) is added through the distillation column.

10. The method according to any one of claims 6 to 7, Its features The methyl methacrylate of formula (III) is introduced into the transesterification reaction in the following manner: In the form of a mixture of methyl methacrylate of formula (III) and methanol, The mixture has a methanol concentration less than or equal to that of the azeotropic composition of the methanol and methyl methacrylate of formula (III).

11. The method of claim 10, wherein the mixture is obtained by a prior transesterification reaction involving the formation of methanol.

12. The method according to any one of claims 6 to 7, Its features In the alkyl methacrylate of formula (II) and the alcohol of formula (I), R 1 It is a straight-chain or branched alkyl group having 7 to 20 carbon atoms.

13. The method of claim 12, wherein the R 1 It is a straight-chain or branched alkyl group having 8 to 18 carbon atoms.

14. The method according to any one of claims 6 to 7, Its features The (meth)acrylate of formula (II) is 2-ethylhexyl methacrylate, the (meth)acrylate of formula (III) is methyl methacrylate, and the alcohol of formula (I) is 2-ethylhexanol.

15. The method according to any one of claims 6 to 7, Its features Add the alcohol of formula (I) at a temperature of 0°C to 70°C.

16. The method according to any one of claims 6 to 7, Its features The transesterification was carried out in the presence of a catalyst.

17. The method of claim 16, wherein the catalyst is selected from alkyl titanate, zirconium acetylacetonate, dialkyltin compound, lithium compound, calcium compound or combination thereof; and / or the catalyst is present in an amount of 0.2 to 10 mmol / mol of alcohol of formula (I).

18. The method according to any one of claims 6 to 7, Its features The transesterification method is carried out in the presence of an inhibitor composition comprising or consisting of at least one phenolic polymerization inhibitor.

19. The method of claim 18, wherein the phenol polymerization inhibitor is hydroquinone, hydroquinone monomethyl ether, or a combination thereof.

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